Service providers often seek to maximize their network up-time and service availability by employing link and node redundancy schemes. In the context of carrier Ethernet, a typical topology is to have an access node (for example Digital Subscriber Line Access Multiplexer (DSLAM)) or a customer edge (CE) device “dual-homed” meaning it is attached to two aggregation switches. This topology provides port, link and node level redundancy for the dual-homed device (DHD).
It is often desirable to prevent Layer 2 forwarding loops in a network using some type of mechanism, such as the Spanning-Tree Protocol (STP). However, in some situations, a DHD is either not capable of running STP or the use of STP does not efficiently scale. For example, if a large number of DHDs are connected to the same provider edge (PE) device pair, the use of STP may not scale efficiently. For these situations, it is desirable to implement a redundancy/resiliency mechanism that is not based on STP. Ethernet Link Aggregation (LAG) schemes using a Link Aggregation Control Protocol (LACP) defined in IEEE Standard 802.3-2005 is one such mechanism.
Unfortunately, link aggregation using LACP as defined in IEEE standard 802.3-2005 only works between two back-to-back nodes and is not an option for DHDs connected to a pair of aggregation switches.